Influence of the structural properties and W/Nb ratio upon the photocatalytic activity of tungsten-doped potassium sodium niobate-based perovskites

Abstract

A key challenge in photocatalytic pollutant degradation lies in enhancing the efficiency of perovskite-based catalysts prepared under mild experimental conditions. The incorporation of tungsten (W) into nanostructured hollow particles of alkali niobates was studied as a strategy to improve photocatalytic activity. X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), N2 adsorption/desorption isotherms, Raman and UV–Vis spectroscopies confirmed the successful formation of W-doped K0.5Na0.5NbO3 hollow spherical particles with a monoclinic perovskite structure. Detailed analysis by Rietveld refinement revealed improved octahedral distortion induced by W doping. The photocatalytic activity was evaluated using the molecular density of adsorbed azo dye and the first-order apparent rate-constant, revealing that W-doped samples demonstrated significantly higher activity (3.31×10–2 molecules·nm–2·min–1) compared to the host structure (1.05×10–2 molecules·nm–2·min–1). Based on scavenger tests and mass spectroscopy analysis, a mechanism for the photocatalytic oxidation of the azo dye is proposed.